/*
 * EAP common peer/server definitions
 * Copyright (c) 2004-2012, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "wpa/includes.h"
#include "wpa/common.h"
#include "eap/eap_defs.h"
#include "eap/eap_common.h"

/**
 * eap_hdr_len_valid - Validate EAP header length field
 * @msg: EAP frame (starting with EAP header)
 * @min_payload: Minimum payload length needed
 * Returns: 1 for valid header, 0 for invalid
 *
 * This is a helper function that does minimal validation of EAP messages. The
 * length field is verified to be large enough to include the header and not
 * too large to go beyond the end of the buffer.
 */
int eap_hdr_len_valid(const struct wpabuf* msg, size_t min_payload)
{
    const struct eap_hdr* hdr;
    size_t len;

    if (msg == NULL) {
        return 0;
    }

    hdr = wpabuf_head(msg);

    if (wpabuf_len(msg) < sizeof(*hdr)) {
        wpa_printf(MSG_INFO, "EAP: Too short EAP frame");
        return 0;
    }

    len = be_to_host16(hdr->length);

    if (len < sizeof(*hdr) + min_payload || len > wpabuf_len(msg)) {
        wpa_printf(MSG_INFO, "EAP: Invalid EAP length");
        return 0;
    }

    return 1;
}


/**
 * eap_hdr_validate - Validate EAP header
 * @vendor: Expected EAP Vendor-Id (0 = IETF)
 * @eap_type: Expected EAP type number
 * @msg: EAP frame (starting with EAP header)
 * @plen: Pointer to variable to contain the returned payload length
 * Returns: Pointer to EAP payload (after type field), or %NULL on failure
 *
 * This is a helper function for EAP method implementations. This is usually
 * called in the beginning of struct eap_method::process() function to verify
 * that the received EAP request packet has a valid header. This function is
 * able to process both legacy and expanded EAP headers and in most cases, the
 * caller can just use the returned payload pointer (into *plen) for processing
 * the payload regardless of whether the packet used the expanded EAP header or
 * not.
 */
const u8* eap_hdr_validate(int vendor, EapType eap_type,
        const struct wpabuf* msg, size_t* plen)
{
    const struct eap_hdr* hdr;
    const u8* pos;
    size_t len;

    if (!eap_hdr_len_valid(msg, 1)) {
        return NULL;
    }

    hdr = wpabuf_head(msg);
    len = be_to_host16(hdr->length);
    pos = (const u8*)(hdr + 1);

    if (*pos == EAP_TYPE_EXPANDED) {
        int exp_vendor;
        u32 exp_type;

        if (len < sizeof(*hdr) + 8) {
            wpa_printf(MSG_INFO, "EAP: Invalid expanded EAP "
                       "length");
            return NULL;
        }

        pos++;
        exp_vendor = WPA_GET_BE24(pos);
        pos += 3;
        exp_type = WPA_GET_BE32(pos);
        pos += 4;

        if (exp_vendor != vendor || exp_type != (u32) eap_type) {
            wpa_printf(MSG_INFO, "EAP: Invalid expanded frame "
                       "type");
            return NULL;
        }

        *plen = len - sizeof(*hdr) - 8;
        return pos;
    } else {
        if (vendor != EAP_VENDOR_IETF || *pos != eap_type) {
            wpa_printf(MSG_INFO, "EAP: Invalid frame type");
            return NULL;
        }

        *plen = len - sizeof(*hdr) - 1;
        return pos + 1;
    }
}


/**
 * eap_msg_alloc - Allocate a buffer for an EAP message
 * @vendor: Vendor-Id (0 = IETF)
 * @type: EAP type
 * @payload_len: Payload length in bytes (data after Type)
 * @code: Message Code (EAP_CODE_*)
 * @identifier: Identifier
 * Returns: Pointer to the allocated message buffer or %NULL on error
 *
 * This function can be used to allocate a buffer for an EAP message and fill
 * in the EAP header. This function is automatically using expanded EAP header
 * if the selected Vendor-Id is not IETF. In other words, most EAP methods do
 * not need to separately select which header type to use when using this
 * function to allocate the message buffers. The returned buffer has room for
 * payload_len bytes and has the EAP header and Type field already filled in.
 */
struct wpabuf* eap_msg_alloc(int vendor, EapType type, size_t payload_len,
        u8 code, u8 identifier)
{
    struct wpabuf* buf;
    struct eap_hdr* hdr;
    size_t len;

    len = sizeof(struct eap_hdr) + (vendor == EAP_VENDOR_IETF ? 1 : 8) +
          payload_len;
    buf = wpabuf_alloc(len);

    if (buf == NULL) {
        return NULL;
    }

    hdr = wpabuf_put(buf, sizeof(*hdr));
    hdr->code = code;
    hdr->identifier = identifier;
    hdr->length = host_to_be16(len);

    if (vendor == EAP_VENDOR_IETF) {
        wpabuf_put_u8(buf, type);
    } else {
        wpabuf_put_u8(buf, EAP_TYPE_EXPANDED);
        wpabuf_put_be24(buf, vendor);
        wpabuf_put_be32(buf, type);
    }

    return buf;
}


/**
 * eap_update_len - Update EAP header length
 * @msg: EAP message from eap_msg_alloc
 *
 * This function updates the length field in the EAP header to match with the
 * current length for the buffer. This allows eap_msg_alloc() to be used to
 * allocate a larger buffer than the exact message length (e.g., if exact
 * message length is not yet known).
 */
void eap_update_len(struct wpabuf* msg)
{
    struct eap_hdr* hdr;
    hdr = wpabuf_mhead(msg);

    if (wpabuf_len(msg) < sizeof(*hdr)) {
        return;
    }

    hdr->length = host_to_be16(wpabuf_len(msg));
}


/**
 * eap_get_id - Get EAP Identifier from wpabuf
 * @msg: Buffer starting with an EAP header
 * Returns: The Identifier field from the EAP header
 */
u8 eap_get_id(const struct wpabuf* msg)
{
    const struct eap_hdr* eap;

    if (wpabuf_len(msg) < sizeof(*eap)) {
        return 0;
    }

    eap = wpabuf_head(msg);
    return eap->identifier;
}


/**
 * eap_get_id - Get EAP Type from wpabuf
 * @msg: Buffer starting with an EAP header
 * Returns: The EAP Type after the EAP header
 */
EapType eap_get_type(const struct wpabuf* msg)
{
    if (wpabuf_len(msg) < sizeof(struct eap_hdr) + 1) {
        return EAP_TYPE_NONE;
    }

    return ((const u8*) wpabuf_head(msg))[sizeof(struct eap_hdr)];
}
